Flashback-resistant blowpipe



Feb. 22, 1938. w. J. JAcoBssoN FLASHBACK RESISTANT BLOWPIPE- Filed Aug. s1, 1932 4 Sheets-Sheet 1 INVENTOR ATTORNEY Feb. 22, W L JAIQQBSSQN 2,108,819

FLA'SHBACK RESISTANT BLOWPIPE Filed Aug. 31, v1932 I 4 Sheets-Sheet 2 1 llt.

' l INVENTOR ATTORN EY Feb. 22, 1938. w J, JACQBSSON 2,108,819

I FLASHBAGK RESISTANT -BLOWPIPIE: l

v Filed Aug..I s1, 1932 Sheets-sheet 3 iik@ ATTORNEY Feb. 22, 1938. w. J. JAcoBssoN FLASHBACK RESISTANT BLOW'PIPE Filed Aug. 31, 1952 4 Sheets-Sheet 4 Patented Feb. '22, 193s4 PATENT @FFECE Wilgot .ll. .acobssom Buiiialo, N. Y., assigner, by

mesne assignments, to tlnion Carbide andl @ar- 'bon Corporation, a corporation ci New Yorba Applicationdngust 3l, i932, Serial No. wit@ malins.

My invention relates to blowpipes adapted to utilize oxygen and a combustible gas for producing a heating flame. The invention relates particularly to the construction of the gas conit duits for preventing ila hbacksin the blowpipe. When a blowpipe isf/functioning properly the iiame produced by the stream of combustible gas issuing from the end of a blowpipe nozzle is separated from the discharge orifice Ain the nozzle 10 kby an unburned portion of the gas stream. Ii; the propagation of the ilame towards the orifice is greater than thevielocity of thegas stream, the flame travels bacward along the unburned portion of the gas st eam y,and recedes into the l vcombustible gas mixt rev passage. The momentaryrecession of the 1 ame into the combustible mixture passage lis kn n asa backilre and this phenomenon 1s usuallyt accompanied by a sharp explosion. If the llame continues to burn with- 90 in the combustible gas ture passages this phenomenon is known asY ilashback which pro.- duces a sizzling noise wit the blowpipe. Un-

der a given set of conditiol s the direct ratioot the number of backiires. to t e number of flash- 5 backs is known as the flashback resistance of a blowpipe. l

When a ilashback occurs it is necessary to cut off at least one of the llame supporting vgases to extinguish the flashback/name. During the 30 period of the flashback and'up untilthe time the ilame is rellghted and adjusted the blowpipe is rendered inoperative. used for welding, the strength of the' weli is deleteriously affected due to the cooling of the weld d uring the inoperative period and also due I'to the ,subsequent reheating-of the weld. If the blowpipe is being used for` cutting, the cut may be lost or made ragged as a result ofthe iiame being extinguished. In any event, time and gas are 40 wasted during the inoperative period oi the blowpipe.

Heretofore it has been proposed to extinguish the backfiring ame by means of baffles or other constrictions placed in the gas passages.

45 devices offer a resistance to the normal vforward flow of the gases and are therefore objectionable.

An object of my invention is to increase the flashback resistance of a blowpipe without in- 50 creasing the resistance to the ilow of the gases through the blowpipe passages.

rIfhe preferredv means of accomplishing the foregoing object is by constructing that portion of either the oxygen passage' or the combustible 55 gas passages or both of said passages extending Such (Gi. ld-WAH rearwardly from the discharge end of the mixer nozzle to a minimum distance from the end of said nozzle so that said portion of said passages is free from constrictions adapted to substantially retard the backward ilow of the gas therein from the mixing tube throat and by proportioning the length and volume of said portion of said gas passages in accordance with the pressurein the mixing tube throat produced by backres and also in accordance with the consumption of the acetylene by the blowpipe.

The above and other objects will be more clearly understood from the following descrip- -tion and accompanying drawings, in which Flg. I is a top view of a blowpipe disclosing one l. embodiment of my invention.

Fig. II is a longitudinal cross-section of the blowpipe along the line II-II in Fig. I;

Figs. HI, IV, V, and VI are enlarged crosssections of the blowpipe taken on the lines III-III l to VI--VI respectively in Fig. I;

Fig. VII is an enlarged sectional view taken on the .line VII-VII in Fig. II.

Figs. VIII and IX are respectively topand rear end views of a modification of the blowpipe shown in Figs. I to VII.

Fig. X is a longitudinal view of the blowpipe showing some .of the elements in section along the line X-X in Fig. VIII.

Figs. XI to XIIIare cross-sectional views along the lines XI to XIII respectively in Fig. X.

Figs. XIV and XV- are respectively sectional views of the valve body on the lines XIV- XIV and XV-XV as shown in Fig. IX.

Fig. XVI is a diagrammatic illustration of my invention in its general aspects.

My invention is illustrated herein in reference to metal cutting blowpipes, .that is, blowpipes utilizing a preheating iiame and a highly oxidizing stream of gas for removing metal. blowpipe disclosed in the modiication shown in Figs. I to VII comprises a handle I having a rear valve body 2 and a forward valve body 3 provided with valves for controlling the cutting and heating gases discharged from theblowpipe head 4. The blowpipe is supplied with oxygen through a hose (not shown). which is attached to a nipple 5. The nipple 5 is'connected to the rear valve body 2 and the passage in the nipple communicates with a passage 6 in .the rear valve 50 body 2. A valve I in the passage 6 controls the ilow of oxygen therein. A tube 8 connects the passage 6 in the rear valve body 2 with an inlet passage 9 in the forward valve body 3.

The oxygen inlet passage 9 in the forward valve 55 the stem I8 of the cutting valve I2 which con-v trols the flow of the oxygen from the valve chamber inlet I 1 to the outlet I8 which is connected to a tube I8 leading from the forward valve body 3 to a cavity 28 in the blowpipe head 4.

A nozzle 2l is connected to the blowpipe head 4 by a clamping nut 22. The nozzle 2i has a central cutting oxygen passage 23 therethrough which is connected to the cavity 28 in the blowpipe head 4.

My invention Apertains particularly to the conduits for conducting the heating oxygen and combustible gases and the mixture of these gases to the discharge end of the burner nozzle 2l and how they are constructed to prevent flashbacks. 'I'he construction of these passages depends upon a number of conditions which will be hereinafter explained. 'I'he blowpipe shown in Figs. I to VII is illustrative of a medium pressure blowpipe.` that is, a blowpipe using up to 15 lbs. pressure in the acetylene hose. As shown therein the branch heating oxygen passage IIin the forward valve body 3 is provided with a heating oxygen control valve 24 for controlling the iiow of the heating oxygen from the valve inlet chamber 25 to the valve outlet chamber 26 which communicates with a rearwardly extending conduit 2l which is connected to one end of a coiled tube 28 enclosed in the blowpipe handle i I'he other end of the coiled tube 28 is connected to one end of -a return conduit 28 and the other end of the return conduit 28 is connected to a passage 38 in the forward valve body 3. The passage 38 leads to the rear portion of the gas mixer 3l. In this case the heating oxygen control valve 24 is the -iirst point nearest the mixer nozzle which oHers passage determines 'the ashback resistance of the blowpipe. 'Ihe coiled tube 28 is inserted in the passage as a convenient means for obtaining the desired length of and volume in the passage between the end 32 of the mixer nozzle and the nearest point-.of resistance to the backward iiow to permit the desired recession of backflring gases into said passage for the prevention of ilashbacks as will be hereinafter explained.

The mixer 3| comprises a bore 34 formed in the bottom portion of the forward valve body 3. A portion of the mixer bore 34 is screwthreaded to receive a threaded locking ring 33a which bears against the rear end of the mixer nozzle 33 which'is thereby secured in the mixer bore 3'4. The end of the mixer bore 34 is closed by a screw-threaded plug 3l.

A combustible gas such as acetylene is supplied to the gas mixer 3| through a gas hose (not shown) which maybe attached tp a nipple 38 which is attached to the rear valve body 2. The passage inthe nipple 34 communicates with a passage 31 in the rear valve body 2. v.I'leillllsl' 2,1os,sio

of combustible gas in the e 31 is controlled by a cut-oit valve 38. The combustible gas passage 31 in the rear valve body 2 communicates with a tube 38 which connects the passage 31 to a combustible gas passage 48 in the forward valve body 3. 'Ihe latter passage 48 leads to the annular combustible gas chamber 4| in the mixer 3i.

The heating oUgen isdischarged from the forward end 32 of the mixer nozzle 33 through a'central e 42 therein. The oxygen discharge from the end of the nozzle 33 mingles with the combustible gas which flows from chamber 4I around the end of the mixer nozzle 33 and the two gases iiow from the mixer outlet or throat 43 to a mixing tube 44 connected at one end to the forward valve body 3. I prefer to make the central passage 42 in the mixer nozzle as large as the mixer throat 43 so that in the event of a backfire the gases in the throat can pass backward into the central mixer passage 4t in the blowpipe nozzle 2l at the end of which thel mixture may be ignited in the usual manner to produce a heating iiame.

A similar type of blowpipe is shown in Figures Y VIII to XV but the tubes are arranged in a different manner. 'For the purpose of rendering the blowpipe flashback resistant. the required length of and volume in the heating oxygen conduit between the heating oxygen control valve and the end of the mixer nozzle is obtained by extending the preheating oxygen conduit from -the control valve to the blowpipe head and returningthe conduit to a mixer located a determineddistance from the blowpipe head.

In the blowpipe shown in Figs. VIII to XV the oxygen is supplied thereto through a nipple 58 and a connecting nut 8l connected in series to a valve body 52 at the rear end oi' the blowpipe handle 53. A cutting oxygen valve 54 is retained in a valve chamber 88 in,y the valve body 82 by means of the connecting/ nut Il screwed into a counterbore at the outer end of the valve chamber 5S. A spring 58 is compressed between the inner end of the connecting nut 8l and the outer end of the valve 84 and normally retains the valve on its seat 51. A central bore" through the connecting nut conducts oxygen from the nipple 88 to the valve chamber II.

Oxygen for cutting purposes may be released from the valve chamber 88 by depressing a cutting oxygen valve lever 53 pivoted onV a pin 88 Ain a block 8l at'thei'orward end of the handle 83. Movement of the lever $8 is transmitted to the cutting oxygen valve 34 through a motion transmitting mechanism comprising a link l2 pivoted at one end to the lever 88 and at the other end to one arm of a bell-crank lever 63 which is pivoted on a pin 33a in a block 84 in the blowpipe handle 33. Motion is transmitted from the other arm of the bell-crank lever 43 to a`rod 4i which extends from the arm or the' bell-crank lever to the cutting oxygen valve I4. The rod 88 is slidably supported in a plug 38 which closes an opening in the wall of the outlet ve 81 of the valve seat I1.

Upon depressing the cutting oxygen valve lever n the cuttingoxygen valve 844s pushed am head. A Acutting nozzle 'l2 is 'secured to the blowpipe head by a clamping nut 13. A central oxygen passage 1t is formed in the nozzle which receives oxygen from the cavity 1| and delivers it to the metal to be cut.

tween the two points through a` heating oxygen is conducted through a T5 which branches off 'The heating oxygen passage from the main oxygen passage 58 in the cutting valve chamber 55 as shown in Fig. XI. A valve 'it is located in the heating oxygen passage 'l5 in the valve body 52 to control the supply of heating oxygen delivered to the gas mixer'll.

In order to obtain the desired length and volume in the passage between the heating oxygen control valve F8 and the discharge end 'I8 of the mixer nozzle l!! to prevent flashbacks, the oxygen is conducted Afrom the outlet passage 8U of the control valve 'i8 to the blowpipe head 'l0 through a tube 8l which extends between the outlet passage 8G in the valve body 52 to a transverse bore 82 in the blowpipe head. The heating oxygen is then returned from the transverse bore 82 to a chamber 83 in the rear end of the mixer bore 84. The oxygen is conducted betube 85 which extends between the transverse bore 82 in the blowpipe head 18 and the valve body 52 which is provided with a passage 85 which conducts the oxygen from the tube 85 to the chamber 83 in the rear end 'of the mixer bore 84 closed by a plug 81 screw threaded therein.

A combustible gas such as acetylene is supplied to the gas mixer 'l1 through a nipple 88 which is connected to a combustible gas valve casing 89 having a valve 90 therein for controlling the ow of gas therethrough. The outlet of the valve casing 89 is connected to a passage 9| in the Valve body 52 `which leads to the annular chamber 92A in the gas mixer 11.

The heating oxygen discharged from the chamber 83 in the rear end of the mixer bore 84 passes through a central bore 93 in the mixer nozzle T9 and mixes with the combustible gas which flows from the annular combustible gas chamber 92 in the mixer 111. The oxygen mixes with the combustible gas and forms a gas mixture which is conducted from the mixer 'l through a tube 84 which is connected to a distributing chamber 95 in the blowpipe head 18. The combustible gas mixture flows from the distributing chamber 95 through the combustible gas mixture passage 96 in the blowpipe nozzle 12. The mixture may be ignited for heating purposes in the usual manner upon being discharged from the blowpipe.

The foregoing illustrates two examples of the application of my invention to a blowpipe adapted -to utilize medium pressure yacetylene with a mixer nozzle having little or no injector `action or in a case where the backfiring'gases are forced backward into the heating oxygen passage for the purpose of preventing flashbacks. The more general application of my invention is diagrammatically illustrated in Fig. XVI. Itis here Ashown that my invention is also applicable to a blowpipe utilizing low pressure acetylene or other combustible gas with an injector mixer nozzle in which case the backring gases are forced up the ing rearwardly from combustible gas passage for the purpose of preventing flashbacks.

As illustrated in Fig. XVI the blowpipe is adapted for use with both systems and for convenience only the heating gas passages are shown. The oxygen is supplied to the blow-pipe through the hose O. The oxygen is controlled by the valve V. The valve V may form the nearest constriction in this passage to the mixing point M in the mixer. the valve V is'placed inrear of such a constriction Co, the inlet to a reservoir R0. The reservoir R0 is inserted in the passage D0 between the constriction Co and the mixing point M as a substitute for the coiled tube 28 in Figs. I to VII and as a means of reducing the length of the corresponding tube in Figs. VIII to XV. The

The location of the elements inl the combustible gas passage De correspondsto and may perform the same function as the corresponding elements in the heating oxygen passage Do in the event the backring gases travel backward into the passage De, but the length and/or volume of the passage Da should be made greater under like conditions. Upony mixing at the mixing point M the combustible mixture of oxygen and a combustible gas flows through the combustible mixture passage Dm to the discharge end of the burner nozzle N. l As herein used the word constriction'indica-tes a point such as Co or" Ca nearest to the mixing point which offers a material resistance to the backward flow of gases and other than the re-` sistance due to normal tube wall friction. The passage D0 is the heating oxygen passage extendthedischarge end of the mixer nozzle, that is, from the mixingvpoint to the nearest constriction which in the usual case is the heating oxygen valve. Da indicates a portion of the combustible gas passage situated in a manner corresponding to D0. Dm is the combustible mixture passage extending from the mixing point to the end of the burner nozzle N.

By properly proportioning the length and volume of the passages Dm, D0 and Da in respect t0 each other for a given combustible gas consumption, a blowpipe having good flashback resistance can be obtained. These proportions may be determined upon the following principles. A backfire produces pressure in Dm and will force the burning, burned and unburned mixture up either the oxygen passage D0 or the combustible gas passage Da or both of said passages'depending uptn the pressure created thereby in the mixing tube throat. and the resistance offered to the backward ow oi the gases in the passages De and De. When the backfring gases are forced backward into either the oxygen passage Do or the combustible mixture passage Da. the further formation of a combustible mixture is prevented until thebackre gases are forced forwardly out of each of l'he passages D@ and DB. If a suicient time elapses between the recession of the backflring gases into the passages D0 and Da and the return of these gases to the mixing point to permit them to be burned out or extinguished before the last of the backiring gases return to the mixing point, then there will be no ashback unless the mixing tube or particles of carbon remaining therein are heated up to the ignition point of the gases. The elapsed time is increased as the pressure in the mixer throat is increased and as the resistance beyond the throat is dere in the mixing tube throat has been increased and good flashback resistance has been obtained with reduced lengths and volumes in the gas passages Do or Da.

`The resistance offered to the backward ow of the backring gases in the oxygen passage and combustible gas passage is increased by constrictions in these passages within a minimum distance back from the mixing point or the discharge end of the mixer nozzle. The resistance to the backward ilow of the baci-:firing gases in the passages Da and D. is also increased by an increase in the normal pressure of the gases in those passages and by a decrease in the volume in the passages Do and/or Ds below a certain minimum for a given length and pressure therein. When a backfire occurs the backring gas will travel most readily into the passage offering the least resistance.

From the standpoint of preventing flashbacks it isdesirable that the backring gases travel backwards into the oxygen passage D in preference to the combustible gas' passage D. and that the unburned mixture be retained in the oxygen passage D0 until it has been completely burned and until after the combustible gas has resumed its forward ow and returned to the mixing point. However, blowpipes can be made flashback resistant by causing' the backiring gases to travel backward into the combustible gas passage until the mixture is completely burned out before re- ,turning to the mixing point and after the return of the'oxygen to said point. .As the combustible mixture burns more slowly in the combustible gas passage than itdoes in the oxygen passage, it is necessary to retain the combustible mixture in the combustible gas passage Di a. greater period of time to allow it tocompletely burn 4before returning to the mixing point than it is necessary .to retain the combustible mixture in the oxygen passage D0 under like conditions. Furthermore when the oxygen returns to the point of mixing vbefore the combustible gas arrives, it may susthe foregoing explanation it is necessary to delay L the return to the mixing point of only the last component of the combustible mixture which reaches themixing point after a backfire until after the flame in that component has been ex.-

tinguished and until after any matter containedin the mixing tube and in the vicinity of themixing point has been cooled below the temperatureof ignition of the combustible mixture, although ifl desired the return of both components of the combustible mixture to the mixing point may be delayed as shown in Fig. XVI to obtain good flashback resistance.

Referring to Fig. XVI in connection with the examples A, B, and C shown in the table below, in the case of a blowpipe utilizing medium pressure acetylene with a consumption up to 50 cu. it. of acetylene per hour excellent flashback resistance was obtained. In these examples no provision was made for the backilring gases to re- .ilcede into the acetylene passage. 'Therefore this passage was constructed as usual. ample the length of Dm was 7" and its volume was .16 cu, in.

v l, A B C Ds Length in inches--- l3. 8 17. 6 19. 6 D. Volume in cu. inches 33. 70 9.00 3. 47 1 Length in inches 3.8 7. 6 9. 6 d, Volume in cu. inches l 35 45 In each 'of the above examples when do was reduced in length by more than one inch, thereby reducing D0 by the same amount, the flashback resistance was lowered. -I have found that the length and volume of the passage Do and also Dn may be increased without reducing the ashback resistance of the blowpipe.

I have also found that-when the cu. ft. of consumption of acetylene is increased in a blowpipe designed to give good flashback resistance for a certain maximum consumption and a minimum length and volume in the passages. Da or D; for a given Dm that the length and/or volume in the passages D., D or Dm must be increased to obtain the same degree of ashback resistance.

While I have illustrated my invention in connection with a cutting blowpipe, my invention is equally applicable to welding blowpipes and the invention may be applied to either the oxygen or the combustible gas passage for preventing ashbacks. Also a wide departure may be made from the examples as given herein. I therefore wish to limit my invention only by the scope of In each exthe claims appended hereto. l L

I I claim:

1. A'iiashback resistant blowpipe adapted to utilize a combustion supporting gas and a combustible gas for producing a heating ilame, said ing directly with said mixer mozzle and being elongated and having a minimum internal crosssectional area substantialy as large as the internal area of said mixer throat; said elongated' portion being free from constrictions therein and having suiilcient length and volume therein to receive the unburned backring combustible mixture and to retain said backiiring combustible mixture therein until said mixture has' been completely burned and until said combustible mixture conduit and any particles remaining therein have been cooled below the ignition temperature o of said combustible mixture.

2. A whack-resistant blowpipe adapted to utilize a combustion supporting gas and a combustible gas for producing a heating flame, said blowpipe comprising a burner nozzle; a mixer; a conduit for conducting the combustible gas mixture to said burner nozzle; a supply conduit fcr conducting a combustion supporting gas to said mixer; a supply conduit for conducting a. combustible gas to said mixer; a portion of one of said supply conduits connecting directly with said mixer and being elongated; said elongated portion being free from constrictions and having sufficient length and internal capacity to freely receive an unburned backring combustible mixture and retain the same therein until completely burned, and until said combustible mixture conduit and any particles of carbon therein have cooled below the ignition temperature of said combustible mixture.

3. A ilashback-resistant blowpipe comprising a Y burner nozzle; a gas mixer; a conduit for conducting a combustion-supporting gas to said mixer; a conduit for'conducting a combustible gas to said mixer; a conduit for conducting a combustible gas mixture from said mixer to said burner nozzle; a portion of one of said rst two conduits immediately in the rear of said mixer being elongated and free from constrictions adapted to substantially retard the backward ow of gas therein and having suiiicient length and internal capacity to freely receive an unburned backring combustible mixture and retain the same therein until completely burned, such elongated portionV including a coil, and the other or said two conduits having a part thereof surrounded bysaid coil. l'

4.111 a flashback-resistant blowpipe, the combination of a blowpipe head; a burner nozzle secured to said head; a Valve body; a gas mixer within said `valve body; a handle secured to said valve body; means for conducting a combustible mixture from the outlet of said' mixer to said burner nozzle, such conducting means including a tube secured to said head and to said valve body; a conduit -for supplying a combustible gas to said mixer; a conduit for supplying a-combustion-supporting gas to said mixer; and valves mounted on said valve body and severally controlling the flow of gas through said conduits, one of said conduits being elongated between its control valve and said mixer and including a coil within said handle, such elongated conduit being free from constrictions adapted substantially to' retard the backward now of gas therein and mixer; and valves mounted having sufdcient length and internal capacity to receive an unburned backiring combustible mixture and retain said backfiring combustible mixture therein until completely burned, and until such combustible mixture conducting means and 4 any particles of carbon therein have cooled below the ignition temperature of the combustible mixture. I

5. A'ashback-resistant blowpipe comprising a handle; a gas mixer carried by said handle and including a mixer nozzle; a blowpipe head secured to but spaced from said handle; a burner nozzle connected to said head; a conduit for conducting a combustible gas mixture from the outlet of said mixer to said burner nozzle; a valve carried by said handle and controlling the supply-of heating oxygen to said mixer; and a conduit for `such heating oxygen extending from said valve to said head and returning to the inlet of said mixer nozzle, suchheating oxygen conduit being free from constrictions and having sufficient length and internal capacity to receive an unburned backring combustible mixture and retain the same therein until completely burned.

6. In a ashback-resistant blowpipe, the combination of a blowpipe'head having a bore; a

burner nozzle secured to said head; a valve body; a gas mixer carried by said valve body; means for conducting a' combustiblemixture from said mixer to said burner nozzle, such conducting means including a tube secured to said head and one of said conduits `being elonl to said head in communication with said bore inV I said head, such elongated conduit being free from constrictions and having suilicient length.,

and internal capacity to receive an unburnedsf backring combustible mixture and to retain -said backring combustible mixture therein until completely burned and until such combustible mixture conducting means and any particles Y of carbon therein have cooled below the ignition temperature of the combustible mixture.

WILGOT J. JACOBSSON. 

